Anatomically guided instrumentation for trochlear groove replacement

ABSTRACT

A system for replacing a trochlear groove region of a femur. The system includes a prosthesis that includes a bone contact surface and a periphery that defines an outer perimeter. The bone contact surface has a plurality of protrusions and a spatial configuration with respect to one another. Additionally, the system includes a first template that has a plurality of guide holes and a first periphery that defines an outer perimeter that substantially corresponds with the periphery of the prosthesis. Also, included in the system is a second template that has a plurality of guide holes and a second periphery that defines an outer perimeter that substantially corresponds with the periphery of the prosthesis. The plurality of guide holes of the second template are spatially arranged with respect to the second periphery to substantially match the spatial configuration of the plurality of protrusions of the prosthesis.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of the filing date of U.S.Provisional Patent Application No. 61/768,765 filed Feb. 25, 2013, thedisclosure of which is hereby incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to systems and methods for use inpatellofemoral knee replacement, and in particular, relates topositioning guides and bone preparation tools for preparation of thetrochlear groove of a patient's femur and patellofemoral prostheses forimplantation thereon.

BACKGROUND OF THE INVENTION

The knee joint is a tri-compartmental joint consisting of the medial andlateral compartments which make up the tibiofemoral joint (“TFJ”) andthe patellofemoral compartment which makes up the patellofemoral joint(“PFJ”). The PFJ more specifically includes the patella and thetrochlear groove of the femur. Noninflamatory degenerative jointdisease, such as osteoarthritis, inflammatory joint disease, such asrheumatoid arthritis, traumatic injuries and structural abnormalitiesmay affect any combination of the aforementioned knee compartments.Severe pain may result where the articular cartilage of the patellaand/or the femoral trochlear groove is eroded or otherwise damaged andnatural motion of the patella along the trochlear groove is impeded. Forpatients with erosion or damage confined to the PFJ, or for patientswith a history of chronic patella dislocations, a patellofemoral jointreplacement may offer a beneficial alternative to total jointreplacement. Moreover, a patellofemoral joint replacement generallyprovides pain relief or improved patella tracking while preservingsignificantly more bone than a total joint replacement.

In total joint replacement, all three compartments are effected wherebyportions of a patient's trochlear groove, medial and lateral condyles,and tibial plateau are generally each resected and substituted for byone or more joint prostheses. In contrast, in PFJ replacement, generallyonly the patella and the trochlear groove are replaced. A major benefitof PFJ replacement over total joint replacement is bone preservation,which may reduce recovery time and post-operative pain. Anotheradvantage of bone preservation is that the joint line may be maintainedresulting in a more normal functioning knee. Further advantages mayinclude less cost and procedure duration, which reduces the likelihoodof contracting an infection and positively affects recovery time.

Current PFJ replacement systems employ several types of instruments forremoving bone in the trochlear groove region of the femur. For example,forming bone adjacent the intercondylar notch of the trochlear groovemay occur with a rongeur, osteotome, rasp, reciprocating or oscillatingsaw, burr, or a combination of all of these instruments. However, acommon characteristic of the use of these instruments in current PFJreplacement is that they are generally free-hand instruments thatprimarily rely on the skill of the surgeon handling them. However, evena skilled surgeon may have trouble duplicating results where speed andprecision are critical. Therefore, one of the biggest drawbacks ofcurrent instrumentation is that each provides no true anatomically basedmeans for guiding the surgeon to restore the trochlear groove orpatellar track to ensure proper patellofemoral kinematics. Further,certain existing patellofemoral implants have asymmetric designs and fewsizing options, which frequently results in a poor anatomic fit. Guidedformation of this bone and proper selection of patellofemoral implantsare important for implant stability and sustainability, as well asassuring natural patellar tracking and restoration of the “Q angle”defined by the lines representing the pull of the quadriceps muscle onthe patella and the axis formed by the patella tendon between thepatella and tibial tubercle.

Therefore, there is a need for guided PFJ reconstruction instrumentationthat provides accurate, reproducible results and a varied selection ofanatomic patellofemoral implantation with improved patellar trackingcharacteristics that collectively provide added natural post-operativeknee kinematics.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect of the present invention, a prosthesis forimplantation within a prepared trochlear groove of a femur bone isdisclosed herein. The prosthesis includes a proximal region that has afirst bone contact surface. The first bone contact surface has aplurality of protrusions that extend outwardly therefrom for insertioninto a plurality of bone voids formed in the femur bone. The pluralityof protrusions each have a longitudinal axis that is acutely angled to aplane of the first bone contact surface. The prosthesis further includesa distal region that includes a second bone contact surface. The secondbone contact surface has an annulus projecting outwardly therefrom forinsertion into a bone void formed in the femur bone. The annulus has alongitudinal axis that is perpendicular to a plane of the second bonecontact surface, wherein the plane of the first bone contact surface isangled with respect to the plane of the second bone contact surface.

According to one embodiment of this first aspect, the annulus may berealized in the form of a sidewall defining a cavity therein. Thesidewall may include at least one cut-out about the circumference of thesidewall such that cut-out may be in fluid communication with thecavity.

According to another embodiment of the first aspect, the at least onecut-out may be realized in the form of a plurality of cut-outs that arearranged in a radial array about the circumference of the sidewall ofthe annulus.

According to yet another embodiment of this first aspect, the implantmay include an articular surface opposite the first and second bonecontact surfaces. The articular surface may include a medial and alateral portion, wherein the lateral portion of the articular surfacehas a wider profile than the medial portion of the articular surface.

According to a second aspect of the present invention is a system forreplacing a trochlear groove region of a femur bone. The system includesa prosthesis that includes a bone contact surface and a periphery thatdefines an outer perimeter of the bone contact surface. The bone contactsurface has a plurality of protrusions for insertion into the femurbone. The plurality of protrusions have a spatial configuration withrespect to one another. Additionally, the system includes a firsttemplate that has a plurality of guide holes. Further, the firsttemplate has a first periphery that defines an outer perimeter of thefirst template that substantially corresponds with the periphery of theprosthesis. Also, included in the system is a second template that has aplurality of guide holes. Furthermore, the second template has a secondperiphery that defines an outer perimeter of the second template thatsubstantially corresponds with the periphery of the prosthesis. Theplurality of guide holes of the second template are spatially arrangedwith respect to the second periphery to substantially match the spatialconfiguration of the plurality of protrusions of the prosthesis.

In one embodiment, the bone contact surface of the prosthesis mayinclude a proximal region and a distal region. The plurality ofprotrusions may be at least two protrusions extending from the proximalregion of the bone contact surface and one protrusion extending from thedistal surface. The at least two protrusions may be realized in the formof pegs and the one protrusion may be realized in the form of an annulushaving a sidewall, which defines a cavity therein.

The sidewall may include at least one cut-out about the circumference ofthe sidewall such that the cut-out is in fluid communication with thecavity. The at least one cut-out may be realized in the form of aplurality of cut-outs that are arranged in a radial array about thecircumference of the sidewall of the annulus.

In another embodiment, the first template may further include a proximalregion and a distal region that extends from the proximal region. Theproximal region may have a flat bone engaging surface that includes aplane configured to substantially mate a plane of a resected portion ofthe femur bone. Further, the proximal region of the first template mayinclude a window to view the resected portion of the femur bonetherethrough when the flat bone engaging surface substantially mates tothe resected portion of the femur bone.

Yet another embodiment, the least one of the plurality of guide holes ofthe first template is located in the proximal region, and at least oneof the plurality of guide holes of the first template is located in thedistal region.

Further, the distal region may be arcuate and taper distally from theproximal region and terminate at the periphery of the first template.

According to a third aspect of the present invention is a system forreplacing a trochlear groove region of a femur bone. The system includesa prosthesis that has a bone contact surface and a periphery defining anouter perimeter of the bone contact surface. The bone contact surfacehas a plurality of protrusions for insertion into the femur bone. Theplurality of protrusions have a spatial configuration with respect toone another. Additionally, the system includes a first template that hasa guide opening and a first periphery that defines an outer perimeter ofthe first template that substantially corresponds with the periphery ofthe prosthesis. The guide opening is configured to receive and guide abone punch instrument. Also included in the system is a second templatethat has at least one guide hole and a second periphery that defines anouter perimeter of the second template and that substantiallycorresponds with the periphery of the prosthesis. The at least one guidehole is configured to receive a bone resection tool.

In one embodiment, the bone contact surface of the prosthesis includes aproximal region and a distal region. The plurality of protrusions may beat least two protrusions extending from the proximal region of the bonecontact surface and one protrusion extending from the distal region ofthe bone contact surface. The at least two protrusions may be realizedin the form of pegs and the one protrusion may be realized in the formof an annulus that has a sidewall, which defines a cavity therein.

The sidewall may include at least one cut-out about the circumference ofthe sidewall such that the cut-out is in fluid communication with thecavity. The at least one cut-out may be realized in the form of aplurality of cut-outs that are arranged in a radial array about thecircumference of the sidewall of the annulus.

In another embodiment, the first template may further include a proximalregion and a distal region that extends from the proximal region. Theproximal region may have a flat bone engaging surface that includes aplane configured to substantially mate a plane of a resected portion ofthe femur bone. Further, the proximal region of the first template mayinclude a window to view the resected portion of the femur bonetherethrough when the flat bone engaging surface substantially mates tothe resected portion of the femur bone.

In yet another embodiment, the guide opening may be located in thedistal region of the first template. The distal region may include aflange around the perimeter of the guide opening for smooth insertion ofthe bone punch instrument. Further, the flange may include a recess forreceipt of depth stop tabs of the bone punch instrument.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood with regard to the followingdescription, appended claims, and accompanying drawings where:

FIG. 1A shows a perspective view of a flexion/extension (“F/E”)alignment assembly having an intercondylar block and an F/E stylusassembly.

FIG. 1B shows a side view of the F/E alignment assembly of FIG. 1A.

FIG. 2 shows a perspective view of the intercondylar block of FIG. 1A.

FIG. 3 shows a perspective view of the F/E stylus assembly of FIG. 1A.

FIG. 4 shows a perspective view of an internal/external (“I/E”)alignment assembly having the intercondylar block of FIG. 1A and analignment handle.

FIG. 5 shows a perspective view of an embodiment of a resectionalignment assembly having the intercondylar block of FIG. 1A, aresection guide, and a resection stylus assembly.

FIG. 6 shows a perspective view of the resection guide of FIG. 5.

FIG. 7 shows a perspective view of the resection stylus assembly of FIG.5.

FIG. 8 shows a perspective view of a resection demonstration assemblyhaving the intercondylar block of FIG. 1A, the resection guide of FIG.5, and a blade runner.

FIG. 9 shows a perspective view of the blade runner of FIG. 8.

FIG. 10 shows a perspective view of an implant profiler.

FIG. 11A shows a perspective view of the implant profiler of FIG. 10.

FIG. 11B shows another perspective view of the implant profiler of FIG.10.

FIG. 12A shows a front view of the implant profiler of FIG. 10superimposed on a silhouette of a patellofemoral implant.

FIG. 12B shows another front view of the implant profiler of FIG. 10superimposed on a silhouette of a patellofemoral implant.

FIG. 13 shows perspective view of a reaming step and a reamer.

FIG. 14 shows a perspective view of the reamer of FIG. 13.

FIG. 15 shows a perspective view of a trochlear punch assembly having apunch guide and a multiblade punch.

FIG. 16 shows a perspective view of the punch guide of FIG. 15 situatedwith respect to a femur bone.

FIG. 17 shows a perspective view of the punch guide of FIG. 15.

FIG. 18 shows a perspective view of the multiblade punch of FIG. 15.

FIG. 19 shows a perspective view of a circular rim drill template.

FIG. 20 shows a perspective view of the circular rim drill template ofFIG. 19.

FIG. 21 shows a perspective view of a sizing and pinning step, apunching step and a multifunction assembly having a two-in-one deviceand a uniblade punch.

FIG. 22 shows a perspective view of the two-in-one device of FIG. 21with respect to a femur bone.

FIG. 23 shows a perspective view of the two-in-one device of FIG. 21.

FIG. 24 shows a perspective view of the uniblade punch of FIG. 21.

FIG. 25 shows a perspective view of another embodiment of a drillingstep and a rimless drill template situated with respect to a femur bone.

FIG. 26 shows a perspective view of the rimless drill template of FIG.25.

FIG. 27 shows a perspective view of a sizing and punning step and atrochlear trajectory assembly having a monolithic trochlear trajectoryfinder (“TTF”).

FIG. 28A shows a perspective view of the monolithic TTF of FIG. 27superimposed on a patellofemoral implant.

FIG. 28B shows a front view of the monolithic TTF of FIG. 27superimposed on a patellofemoral implant.

FIG. 29A shows a perspective view of the monolithic TTF of FIG. 27.

FIG. 29B shows another perspective view of the monolithic TTF of FIG.27.

FIG. 29C shows a rear perspective view of the monolithic TTF of FIG. 27.

FIG. 29D shows a side view of the monolithic TTF of FIG. 27.

FIG. 30 shows a perspective view of a captured resection guide.

FIG. 31A shows a front view of an embodiment of an articular surface ofa patellofemoral implant.

FIG. 31B shows a front view of another embodiment of an articularsurface of a patellofemoral implant.

FIG. 32A shows a perspective view of closed circular rim embodiment of abone interface surface of a patellofemoral implant.

FIG. 32B shows a side view of the patellofemoral implant of FIG. 32A.

FIG. 32C shows a cross-sectional view of the patellofemoral implant ofFIG. 32A.

FIG. 32D shows another cross-sectional view of the patellofemoralimplant of FIG. 32A.

FIG. 33A shows a perspective view of an open circular rim embodiment ofa bone interface surface of one embodiment of a patellofemoral implant.

FIG. 33B shows a side view of the patellofemoral implant of FIG. 33A.

FIG. 33C shows a cross-sectional view of the patellofemoral implant ofFIG. 33A.

FIG. 33D shows another cross-sectional view of the patellofemoralimplant of FIG. 33A.

FIG. 34A shows a rimless embodiment of a bone interface surface of apatellofemoral implant.

FIG. 34B shows a side view of the patellofemoral implant of FIG. 34A.

FIG. 34C shows a cross-sectional view of the patellofemoral implant ofFIG. 34A.

FIG. 34D shows another cross-sectional view of the patellofemoralimplant of FIG. 34A.

DETAILED DESCRIPTION

As used herein, the term “proximal” means closer to the heart, and theterm “distal” means further from the heart. The term “anterior” meanstoward the front part of the body or the face, and the term “posterior”means toward the back of the body. The term “medial” means toward themidline of the body, and the term “lateral” means away from the midlineof the body. F/E refers to flexion and extension rotation about theepicondylar axis of a femur bone. I/E refers to internal and externalrotation about the longitudinal axis of the intramedullary canal of afemur bone.

FIGS. 1A and 1B show an F/E alignment assembly 3000 in accordance withan embodiment of the present invention. The F/E alignment assembly 3000includes an F/E stylus assembly 300 and an intercondylar block 200.

FIG. 2 shows the intercondylar block 200, which generally includes alateral-medial (“L-M”) member 204, an anterior-posterior (“A-P”) member214, and a plurality of holes. The plurality of holes includes a centeralignment hole 222, cross pinholes 224, epi-alignment pinholes 206,bossed holes 210, flanking holes 212, and an overhead pinhole 216. Inone embodiment, the intercondylar block 200 is generally cross shapedwherein the L-M member 204 orthogonally intersects the A-P member 214.The intercondylar block 200 also includes a bone interface surface and adistal surface that is opposite the bone interface surface and separatedby the thickness of the intercondylar block. This thickness formsanterior 218, posterior 202, and L-M surfaces 208 that are generallyperpendicular to the bone interface and distal surfaces. The locationswhere these surfaces intersect are preferably rounded to lessen the riskof soft tissue damage.

In one embodiment of the present invention there are two flanking holes212 extending from the anterior surface 218 through the posteriorsurface 202 of the L-M member 204, with each of these flanking holes 212situated on each side of the A-P member 214. The distance of thelongitudinal axis of the A-P member 214 to the center of one flankinghole 212 may be equal to the distance between the longitudinal axis ofthe A-P member 214 to the center of the other flanking hole 212. Each ofthe flanking holes 212 may be orthogonally intersected by a bossed hole210. However, in other embodiments the flanking holes 212 may be angled.Each bossed hole 210 extends from the distal surface of theintercondylar block into a corresponding flanking hole 212, wherein thelongitudinal axis of the flanking hole 212 preferably intersects withthe longitudinal axis of the bossed hole 210. However, the bossed hole210 preferably does not extend through the bone interface surface, butmay extend through the bone interface surface in some embodiments. Eachbossed hole 210 has a boss that extends distally from the distalsurface. Additionally, each bossed hole may include a captured screw220, which may be threaded to extend into and retract out of theflanking hole 212 when a torque is applied to the captured screw 220.The captured screw 220 preferably has a flat surface at the end of itsshank in order to engage and hold a surface of an object inserted intothe flanking hole 212. However, other embodiments may include surfacesof differing shapes, for example a conical point or a rounded edge.

Extending through each of the L-M surfaces 208 is an epi-alignmentpinhole 206. The epi-alignment pinholes 206 preferably terminate priorto extension into a flanking hole 212. However, the longitudinal axis ofeach epi-alignment pinhole 206 preferably, orthogonally intersects thelongitudinal axis of each flanking hole 212. However, other embodimentsmay provide for these axes to be offset from each other. Further, thelongitudinal axis of the epi-alignment pinholes 206 are parallel andpreferably collinear with the longitudinal axis of the L-M member 204.

Located generally at the center of rotation of the intercondylar block200 is the center alignment hole 222, which extends from the distalsurface and may either extend through the bone interface surface orterminate within the intercondylar block 200. An alignment platform 226resides on the distal surface adjacent to the center alignment hole 222.The alignment platform 226 has an upper surface that is preferablyparallel to a tangent line of the center alignment hole 222.

Located in an adjacent end of the A-P member 214 is an overhead pinhole216, which extends from the distal surface through the bone interfacesurface. Located adjacent the opposite end of the A-P member 214 are twocross pinholes 224 that extend through the distal surface and may beoffset from the longitudinal axis of the vertical member. The two crosspinholes 224 penetrate the intercondylar block 200 at an oblique anglewith respect to the distal and bone contacting surfaces. The crosspinholes crisscross each other, but preferably do not intersect.

Referring to FIG. 3, an F/E stylus assembly 300 is shown including ashouldered shaft 304, a housing 316, and an F/E stylus 302. Theshouldered shaft may have a portion that is cylindrical and a portionthat is semi-cylindrical, wherein these portions connect at a shoulder306. The semi-cylindrical portion may have a flattened surface 308 thatextends the length of the semi-cylindrical portion. The cylindricalportion has a larger radius than the semi-cylindrical portion. Thisdifference in radii forms the shoulder 306. One end of the cylindricalportion is rigidly disposed within the housing 316.

The F/E stylus 302 has an F/E stylus shaft 310 which is rotationally andslidably disposed within the housing 316 such that the longitudinal axisof the F/E stylus shaft 310 is perpendicular to the longitudinal axis ofthe shouldered shaft 304. This slidability and rotatability is regulatedby a leaf spring that resides in the housing 316, which providesresistance until a releasing force is achieved. Once the releasing forceis achieved, the F/E stylus shaft 310 may move translationally orrotationally until the force is removed, thus reengaging the resistiveforce of the leaf spring. At one end of the F/E stylus shaft 310 is ahandle 314, which is generally threaded onto shaft 310. The handle 314allows the surgeon to rotate shaft 310 about its longitudinal axis forease of removal from an incision, and improves the surgeon's grip via anergonomic design that has enhanced frictional properties. The other endof the F/E stylus shaft 310 includes an alignment rudder 312. Thealignment rudder has a bone contacting surface that is preferably angledat approximately 90 degrees with respect to the longitudinal axis of theshouldered shaft. In other embodiments, this angle could range from 86to 90 degrees. The alignment rudder 312 is preferably elongated and flatto obtain a more accurate assessment of the planarity of the anteriorcortex of the femur bone 100. In one embodiment, the bone contactingsurface of the alignment rudder 312 may be rounded. In the embodimentillustrated by FIG. 3, the alignment rudder 312 is fixed to the F/Estylus shaft 310. However, in other embodiments the rudder 312 mayrotate about its longitudinal axis.

Referring to FIGS. 1A and 1B, the shouldered shaft 304 is inserted intothe either of the flanking holes 212 such that the F/E stylus shaft 310is centered over the intercondylar block and orthoginal with thelongitudinal axis of the A-P member 214. Thus, the housing 316 spacesthe longitudinal axis of the shouldered shaft 304 from the longitudinalaxis of the F/E stylus shaft 310 at the same distance as thelongitudinal axis of the flanking holes 212 from the longitudinal axisof the A-P member 214. The shouldered shaft 304 is inserted into eitherof the flanking holes 212 wherein the shoulder 306 ensures theintercondylar block is not sitting too far anteriorly. Removal of theshouldered shaft 304 is prohibited by tightening the captured screw 220that intersects the corresponding flanking hole 212 within which theshouldered shaft 304 is inserted. The flattened surface 308 of theshouldered shaft 304 and the flat surface of the end of the capturedscrew 220 engage to provide a solid lock and further ensures the F/Estylus shaft 310 is in proper geometric alignment with the intercondylarblock 200.

FIGS. 1A and 1B also show an F/E alignment step in a patellofemoralarthroplasty. This step aligns the bone interface surface of theintercondylar block 200 with a distal plane 102 formed by the distalfemoral condyles of the femur bone 100 and locks this alignment fromfurther F/E rotation. Alignment is achieved by placing the bonecontacting surface of the alignment rudder 312 in planar contact withthe anterior cortex just proximal of the trochlear groove of the femurbone 100. The bone interface surface of the intercondylar block 200 isthen moved into planar engagement with the distal plane 102 of thedistal femoral condyles by sliding the housing 316 proximally on the F/Estylus shaft 310 until abutment occurs. The 90 degree angle of thealignment rudder 312, the planar reference of the anterior cortex, andthe 90 degree angle between the F/E stylus shaft 310 and the shoulderedshaft 304 ensures that the bone interface surface of the intercondylarblock 200 is planar with the distal plane 102 of the distal femoralcondyles. In other words, the 87 degree angle of the alignment rudder304 along with other geometry of the F/E alignment assembly 3000corresponds with the geometry of a femur bone 100 to confirm distalplanar engagement. Further, the geometric location of the shoulder 306on the shouldered shaft 304 and the geometry of the housing 316 and F/Estylus 302 is such that the intercondylar block 200 is preciselysituated on the distal femoral condyles anteriorly-posteriorly in orderto provide future anatomical reference by other surgical instrumentationin additional bone preparation steps. Thus, when the intercondylar block200 is aligned with the distal plane 102 and the alignment rudder 304 isproperly located on the anterior cortex, the proper anatomical heightalignment is achieved. Alignment medially-laterally is at the surgeon'sdiscretion, but the F/E stylus shaft 310 is generally centered over thetrochlear groove. Once the proper alignment is achieved, a retainmentpin 104 may be driven into the overhead pinhole 216 to lock F/E rotationof the intercondylar block 200. The F/E stylus assembly 300 is thenremoved from the intercondylar block 200 in preparation for an I/Ealignment step.

FIG. 4 shows an I/E alignment assembly 3010 in accordance with anembodiment of the present invention. The I/E alignment assembly 3010includes intercondylar block 200, epi-alignment pins 220, an alignmenthandle 400, and, optionally, a drop rod 402.

The alignment handle 400 generally has a handle portion that isrectangular and one end that includes a cylindrical portion for matingwith the center alignment hole 222 and a triangular portion for matingwith the alignment platform 226. A through-hole may extend through thehandle portion to receive a drop rod.

With the intercondylar block 200 coupled with the distal femoralcondyles via retainment pin 104 inserted into the overhead pinhole 216,an epi-alignment pins 220 is inserted into an epi-alignment pinhole 206and the alignment handle 400 is inserted into the center alignment hole222. The epi-alignment pins 220 are elongated such that they extendbeyond the femur bone's periphery when inserted into the intercondylarblock 200. The epi-alignment pin 220 is preferably inserted medially toreference the medial epicondyle. However, the surgeon may choose toalign with the epi-alignment pins 220 laterally or both laterally andmedially. The alignment handle 400 has a cylindrical portion at one endof the handle, which is inserted into the alignment center hole 222.Adjacent to the cylindrical portion, is a triangular portion that isgenerally an equilateral triangle. When the cylindrical portion isinserted into the center alignment hole 222, one of the sides of thetriangular portion engages the alignment platform 226. A drop rod 402may be inserted through the alignment handle 400 in parallel alignmentwith the longitudinal axis of the A-P member 214 of the intercondylarblock 200.

Once the I/E alignment assembly is brought together, an I/E alignmentstep may be performed. In one embodiment, the surgeon rotates theintercondylar block 200 about the retainment pin 104 located in theoverhead pinhole 216 by applying a torque to the alignment handle 400.Proper alignment is achieved when the epi-alignment pin 220 is visuallyaligned with the epicondylar axis. Alternatively, alignment may beachieved when the drop rod 402 visually aligns with a tibial referenceof the surgeon's preference. This reference may be the tibial shaft,medial malleolus or Whiteside's line of the femur bone 100. Once theappropriate positioning is achieved, the surgeon locks further I/Erotation of the intercondylar block 200 by inserting a retainment pin104 through either one or both cross pinholes 224. The angle of thecross pinholes 224 provides added stability of the intercondylar block200 by, not only prohibiting I/E rotational movement, but alsoprohibiting lift-off of the intercondylar block 200 from the distalfemoral condyles. Also, the angle of the cross pinholes 224 is optimizedto allow the retainment pin 104 to enter into the intercondylar portionof the femur bone 100 in order to avoid damaging the articular surfacesof the femur bone 100 and avoid ligaments. Once alignment and locking isachieved, the epi-alignment pin 220 and alignment handle may be removedin preparation for resection height alignment.

FIG. 5 shows a resection alignment assembly 3020 in accordance with anembodiment of the present invention. The resection alignment assemblyincludes intercondylar block 200, a resection guide 500, and a resectionstylus assembly 600.

FIG. 6 shows an embodiment of the resection guide 500. The resectionguide generally includes a restriction plate 504, a resection plate 514,and a pair of retainment posts 512. Further, the resection guide 500 maybe provided in various sizes based on the size of correspondingpatellofemoral implant. The retainment posts 512 may be semi-cylindricaland may have a flattened surface 508 that runs along the length of eachretainment post 512. Each retainment post 512 is attached to a posteriorside of the resection plate 514. The resection plate has an anteriorresection surface 506 opposite the posterior side. The anteriorresection surface 506 is substantially flat and preferably angled at 4degrees with respect to the distal plane 102 of the distal femoralcondyles when the resection plate 514 interfaces the intercondylar block200. The anterior resection surface 506 may have an extended surface tominimize pivoting and allow for a more accurate cut. The restrictionplate 504 may be attached to the resection plate 514 by a central post510 that connects the anterior resection surface 506 to a posteriorsurface of the restriction plate 504. The central post 510 provides agap between the restriction 514 and resection 504 plates to allow for abone saw to pass through to the femur bone 100. The central post 510 mayhave a rounded triangular shape to facilitate cutting at sharper angles.In other embodiments, there may be two outer posts in lieu of a centralpost. The restriction plate 506 may have a quick connect port 502 thatextends through an anterior side of the restriction plate 504, butgenerally does not extend all the way through the restriction plate 504,however, may extend through in certain embodiments.

FIG. 7 shows the resection stylus assembly 600. The restriction stylusassembly generally includes a quick connect mechanism 610, a housing 604and a resection stylus rod 606. The resection stylus rod 606 is disposedrotationally and slidably within the housing 604. The slidability androtatability of the resection stylus rod 606 is regulated by a leafspring that resides in the housing 604, which provides resistance untila releasing force is achieved. Once the releasing force is achieved, theresection stylus rod 606 may move translationally or rotationally untilthe force is removed, thus reengaging the resistive force of the leafspring. At one end of the resection stylus rod is a handle 608, which isgenerally threaded onto rod 606. The handle improves the surgeon's gripvia an ergonomic design that has enhanced frictional properties. Theother end of the resection guide rod 606 is bent and terminates with astylus tip 602. The end of the stylus tip 602 is rounded and planar withthe anterior resection surface 506 of the resection guide 500 when theresection stylus assembly 600 interfaces with the resection guide 500.

Also attached to the housing is the quick connect mechanism 610.Referring to FIG. 5, the quick connect mechanism is inserted into thequick connect port 502 of the resection guide 500. The quick connectmechanism 610 generally includes a spring-loaded device that engages thequick connect port 502 of the resection guide 500, thereby restrictingremoval of the resection stylus assembly 600 from the resection guide500. However, the quick connect mechanism 610 allows for rotation withinthe quick connect port 502.

Once the resection stylus assembly 600 and resection guide 500 arejoined, a resection height alignment step may be performed. Theretainment posts 508 are inserted into the flanking holes 212 of theintercondylar block 200 such that the flattened surfaces 508 of theretainment posts 512 face the captured screws 220 and the stylus tip 602of the resection stylus rod 606 points toward the anterior cortex of thefemur bone 100. The surgeon may use the handle 608 to manipulate thestylus tip 602 by sliding and/or rotating the resection stylus rod 606within the housing 604 and lifting or pressing down on the handle 608 tochange the height position of the resection guide 500 with respect tothe intercondylar block 200 until the runout of the stylus tip 602interfaces with the lowest point of the proximal end of the trochleargroove of the femur bone 100. Once this is achieved, the dimensionsbetween the stylus tip 602 and the longitudinal axis of the resectionstylus rod 606 and between the longitudinal axis of the resection stylusrod 606 and the portion of the quick connect mechanism 610 thatinterfaces with the restriction plate 504 ensures that the anteriorresection surface 514 is at the proper resection height. This resectionheight is set by locking down the captured screws 220, which locks theresection guide 500 at the proper resection height, thereby achievingproper height alignment.

The proper height alignment may be further verified by demonstrating theresection plane before cutting the femur bone 100. FIG. 8 shows anembodiment of a resection demonstration assembly 3030 according to thepresent invention. The resection demonstration assembly generallyincludes intercondylar block 200, resection guide 500, and a bladerunner 700.

FIG. 9 illustrates an embodiment of the blade runner 700. The bladerunner 700 may include a blade 704 and a finger-grip 702. The blade 704is generally arcuate and flattened and may include an engagement portion706 at one end. The finger-grip 702 is generally disposed adjacent tothe engagement portion 706.

A resection demonstration step may be optionally performed, wherein,with the intercondylar block 200 and resection guide 500 coupled to thefemur bone 100, a surgeon grips the finger-grip 702 and inserts theengagement portion 706 into the gap between the resection andrestriction plates and pivots the blade runner 700 about the centralpost 510 of the resection guide 500 until the blade runner 700 extendsaround the anterior aspect of the femoral condyles. The arcuate shape ofthe blade 704 provides clearance avoid interference with the femur bone100. This provides the surgeon with a visual representation of theresection plane in order to verify that the proper height alignment hasbeen achieved. The surgeon may make fine adjustments to the resectionheight in order to optimize the resection plane location. Once resectionhas been demonstrated to the approval of the surgeon, resection may beperformed with a bone saw through the resection guide 500 to remove aportion of bone from the anterior femoral condyles in preparation toreceive a patellofemoral implant.

Once anterior resection is complete, sizing for a patellofemoral implantand preparation for further bone resection may occur. FIGS. 10-12Bdemonstrate an embodiment of an implant profiler 800. Referring to FIGS.11A-12B, the implant profiler 800 generally includes a proximal portion802 and a distal portion 810 extending therefrom. The proximal portion802 has a bone interface surface that is generally flat in order tosubstantially match the surface of the anteriorly resected femur bone100. The proximal portion also includes an alignment window 804 and abossed pinhole 806 that both extend through the proximal portion 802.The geometry of the periphery of the proximal portion 802 substantiallymatches that of a portion of a patellofemoral implant as demonstrated bya superimposition of the implant profiler 800 on an implant silhouette150 of a patellofemoral implant as seen in FIGS. 12A-B. In other words,the periphery of the proximal portion 802 substantially represents thesize and shape of a portion of a corresponding patellofemoral implant.

The distal portion 810 extending from the proximal portion 802 isarcuate in order to avoid interference with osteophytes and cartilagewhen engaged with the femur bone 100. Further, the distal portion 810 istapered in order to avoid interference with the condyles. The distalportion 802 includes a bossed pinhole 806 that extends through thedistal portion 810. A pair of wings 808 may extend from this bossedpinhole 806 in both the lateral and medial directions. Each wing 808curves into a point that is formed into a contact sphere 812 in order toprevent sharp points from contacting the femur bone 100. The distanceeach wing 808 extends from the bossed pinhole 806 and the distance thedistal portion 810 extends from the proximal portion 802 substantiallymatches the dimensions of the periphery of a portion of a patellofemoralimplant as illustrated by the superimposition of the implant profilerover the implant silhouette 150 of FIGS. 12A-B. Thus, the combination ofthe proximal portion 802 and distal portion 810 of the implant profiler800 ensures that the periphery of the implant profiler 800 substantiallymatches that of a patellofemoral implant in order to appropriately sizethe patellofemoral implant with respect to the femur bone 100.

In the performance of an embodiment of a sizing and pin placement step,a surgeon places the implant profiler 800 over the resected bone suchthat the generally flat bone interface surface of the implant profiler800 planarly engages the anteriorly resected portion of femur bone 100.The window 804 located through the proximal portion 802 provides visualconfirmation that the implant profiler 800 is fully seated and flushwith the anterior resection. The distal portion 810 is placed within theintercondylar portion of the femur bone 100 with the contact spheres 812and the end of the distal portion 810 in contact with the femur bone100. The surgeon, at his or her discretion, determines if the size isappropriate for a corresponding patellofemoral implant. If not, anothersize may be tried until the appropriate size is determined. Once theappropriate size is chosen, the implant profiler 800 is placed on thefemur bone 100. The surgeon then inserts reference pins 106 into theimplant profiler 800 through the bossed pinholes 806. These referencepins 106 are used by other surgical instrumentation as a reference and aguide for resecting the femur bone 100 in order to continue to form thefemur bone 100 to receive a patellofemoral implant as will be discussedlater. Thus, the bossed pinholes 806 of the distal 810 and proximal 802portions of the implant profiler 800 are precisely located within theimplant profiler 800 to correspond with the use of the other surgicalinstrumentation.

A reamer 900 as illustrated by FIGS. 13 and 14 is one of the othersurgical instruments that references the reference pins 106 located bythe implant profiler 800. The reamer 900 generally includes a guideshaft 902, a depth stop 904, and a plurality of cutting blades. Theguide shaft 902 may have a cannulated passageway 910 that extendsthrough the center of the guide shaft 902. One end of the guide shaft902 is adapted to engage a torque applying device, for example a drillchuck. At the other end of the guide shaft 902 resides the plurality ofcutting blades.

According to the embodiment illustrated by FIG. 14, the plurality ofcutting blades include alternating blades 908 that are disposed alongthe circumference of the cutting area. The alternating blades 908alternate in order to provide bone chip clearance so the reamer 900 doesnot become bogged down with bone fragments. The inner blades 906 residealong the cutting area between the alternating blades 908 and thecannulated passageway 910. The inner blades 906 may be offset from theends of the alternating blades 908 so that the alternating blades 908cut deeper into the femur bone 100 than the inner blades 906. The innerblades 906 profile the surface of the femur bone 100 to ensure thesurface of femur bone 100 will be flush or with a patellofemoral implantor slightly below/inside the implant to allow for a cement mantle.Adjacent to the alternating blades is a reaming depth stop 904 that isformed by a rim that protrudes radially from the reamer 900. Thediameter formed by the reaming depth stop 904 is larger than thediameter formed by the alternating blades 908 in order to prevent thereamer 900 from reaming too deeply.

FIG. 13 shows the end of a reaming step. With the reference pins 106 inplace, the cannulated passageway 910 may be placed over the referencepin 106 that had been guided by the bossed pinhole 806 of the distalportion 810 of the implant profiler 800. A torque is delivered to thereamer 900, thereby resecting the femur bone 100 until the reaming depthstop 904 prevents further resection. This may form a void in the femurbone 100 to receive a circular rim of a circular rim implant (discussedlater), or contour the bone surface for more precise engagement with abone interface surface of a patellofemoral implant.

Another surgical instrument that references the reference pins 106located by the implant profiler 800 is a trochlear punch assembly 3040.FIG. 15 illustrates an embodiment of the trochlear punch assembly 3040in accordance with the present invention. The trochlear punch assembly3040 generally includes a punch guide 1000 and a multiblade punch 1100.

FIGS. 16 and 17 show an embodiment of the punch guide 1000. The punchguide 1000 is universal such that one punch guide 1000 may be used forboth knees. The punch guide 1000 generally includes a cylindrical body1002, alignment pinholes 1004, and a pair of blade guides 1006. Thecylindrical body 1002 may have a central passageway that extendstherethrough. A wall may reside within the central passageway providinga depth stop surface 1012 located on each side of the wall. Indicatormarkings 1014 may be disposed on each depth stop surface 1012 toindicate to the surgeon the proper orientation of the punch guide 1000depending on the leg for which the patellofemoral replacement procedureis being performed. The distance from each of the depth stop surfaces1012 to the end of the cylindrical body 1002 forms a rim 1016, whichfacilitates the translational guidance of the multiblade punch 1100. Analignment pinhole 1004 extends through the depth stop surfaces 1012generally through the center of the punch guide 1000. Another alignmentpinhole 1004 is disposed along the external surface of the cylindricalbody 1002 in parallel alignment with the alignment pinhole 1004 locatedwithin the cylindrical body 1002. Grooves 1010 run the length of thecylindrical body 1010 and extend into the central passageway. The bladeguides 1006 extend from the internal passageway through these grooves1010. The blade guides 1006 are angled with respect to each other toform a “V” configuration.

FIG. 18 shows the multiblade punch 1100 according to an embodiment ofthe present invention. The multiblade punch 1100 generally includes ahandle 1104 with an impact region 1102 disposed on one end of the handle1104 and an annular region 1106 disposed on the other end of the handle1104. A cannulated passageway 1110 extends through the annular region1106 into the handle 1104. A pair of punch blades 1108 are tangentiallydisposed on the outer surface of the annular region 1106. The punchblades 1108 are angled with respect to each other to form a “V”configuration that substantially matches the “V” configuration of theblade guides 1106 and to substantially match the periphery of atrochlear region of a patellofemoral implant. The multiblade punch 1100may be monolithic. In another embodiment, the handle 1104 may be modularsuch that it can accept blades that correspond to different sizedpatellofemoral implants.

FIGS. 15 and 16 show a bone punching step. Referring to FIG. 16, thepunch guide 1000 is placed over the reference pins 106 that were locatedby the implant profiler 800. The alignment pinhole 1004 that extendsthrough the center of the cylindrical body 1002 is slid over the mostdistal reference pin 106, and the alignment pinhole 1004 that isdisposed on the outer surface of the cylindrical body 1002 is slid overthe most posterior reference pin 106. The alignment pinholes 1004 andreference pins 106 place the punch guide 1000 in the proper position onthe femur bone 100 as well as at setting the proper rotationalalignment. Where the procedure is being performed on the left leg, thesurgeon will orient the punch guide 1000 such that the indicator marking1014 indicating the left leg is facing the surgeon. Where the procedureis being performed on the right knee, the indicator marking 1014indicating the right knee is set facing the surgeon. As the punch guide1000 is slid over the reference pins 106, the cylindrical body 1002 isinserted into the bone void formed by the reamer 900. Thus, the diameterof the cylindrical body 1002 is dictated by the diameter of the reamer900, which is in turn dictated by the size of the correspondingpatellofemoral implant.

With the punch guide 1000 set in place, the multiblade punch 1100 isguided by the punch guide 1000. The cannulated passageway 1110 of themultiblade punch 1100 is slid over the most distal reference pin 106. Asthis occurs, the annular region 1106 is guided by the rim 1016 formed bythe cylindrical body 1002. Additionally, rotational orientation of themultiblade punch 1100 is guided by the grooves 1010 in the cylindricalbody 1002 and the blade guides 1006. An impulse force is applied to theimpact region 1102 of the handle 1104 until the annular region 1106abuts the depth stop surface 1012, at which point the appropriate punchdepth has been achieved. Once the proper depth is achieved, themultiblade punch and punch guide is removed from the femur bone 100 inpreparation for further bone resection.

FIGS. 19 and 20 show a circular rim drill template 1200 according to anembodiment of the present invention. The circular rim drill template1200 has a bone interface surface and a plurality of holes extendingtherethrough. The plurality of holes include retainment pinholes 1208and drill guide holes 1204. The drill guide holes 1204 may be bossed andmay have a drill stop shoulder 1206 to act as a drill depth stop. Thelength of the boss is determined by the desired depth of cut. Thus, somedrill guide holes 1204 may not be bossed if greater depth is desired.The locations and number of the drill guide holes 1204 within thecircular rim drill template 1200 directly correspond to the locationsand number of bone pegs disposed on a corresponding circular rim implant(discussed later). Generally there are at least two retainment pinholes1208 that have longitudinal axes that may be angled with respect to oneanother in order to prevent lift-off and rotation when coupled to thefemur bone 100. The bone interface surface has a distal portion that mayinclude a circular rim 1210. The bone interface surface may also haveperipheral flanges 1212 extending from the bone interface surface alongthe boundary of the circular rim drill template 1200 for engaging thesection of bone resected by the multiblade punch 1100. The circular rim1210 has a diameter that substantially corresponds to the bone voidcreated by the reamer 900. The periphery of the circular rim drilltemplate 1200 substantially matches the periphery of a correspondingcircular rim implant. In other words, the profile of the circular rimdrill template 1200 is substantially similar to that of a correspondingcircular rim implant such that the surgeon has an accurate visualrepresentation of the size, shape and fit of the circular rim implantwhen he or she drills via the circular rim drill template 1200. Thus,the circular rim drill template 1200 provides the surgeon with anaccurate depiction of the circular rim implant so that he or she canproperly locate the drill guide holes 1204 with respect to the femurbone.

FIG. 19 shows the initiation of a drilling step. The circular rim drilltemplate 1200 is positioned onto the femur bone 100 such that thecircular rim 1210 is disposed within the bone void created by the reamer900. A proximal portion of the bone interface surface planarly engagesthe anterior resected portion of the femur bone 100. Rotation of thecircular rim drill template 1200 is set by the engagement of theperipheral flanges 1212 with the multiblade punched portion of bone.Once the circular rim drill template 1200 is properly seated, thesurgeon inserts retainment pins 108 into the retainment pinholes 1208 toprohibit movement of the circular rim drill template 1200 duringdrilling. The surgeon then drills a series of holes into the femur bone100 through the drill guide holes 1204 to a depth dictated by the lengthof the boss of the drill guide holes 1204. The retainment pins 108 andcircular rim drill template 1200 is removed so that the correspondingcircular rim implant may be implanted on the femur bone 100.

Although the invention thus far has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. The implant profiler 800, reamer 900, trochlear punchassembly 3040, and circular rim drill template 1200 are merely oneembodiment for preparing a femur bone 100 to receive a patellofemoralimplant, more particularly a circular rim implant, for example. However,other instrumentation and methods may be utilized to prepare bone forthe circular rim implant and other embodiments of patellofemoralimplants that would fall align with the principles disclosed herein.

Another exemplary embodiment for preparing bone once anterior resectionof the femur bone 100 has taken place is a multifunction assembly 3050as shown in FIG. 21. The multifunction assembly 3050 is described hereinas corresponding with the preparation of a femur bone 100 to receive arimless implant, for exmample. However, this discussion is merely anexample.

The multifunction assembly 3050 generally includes a two-in-one device1300 and a uniblade punch 1400. FIGS. 22 and 23 illustrate thetwo-in-one device 1300, which generally includes a proximal portion 1302and a distal portion 1310 extending therefrom. The proximal portion 1302has a bone interface surface that is generally flat in order tosubstantially match the surface of the anteriorly resected femur bone100. The proximal portion 1202 also includes an alignment window 1304and at least two retainment pinholes 1206 extending through the proximalportion. At least one of the retainment pinholes 1306 is obliquelyangled with respect to the bone interface surface of the two-in-onedevice 1300 to prohibit lift-off of the two-in-one device 1300 from thefemur bone 100. The geometry of the periphery of the proximal portionsubstantially matches that of a portion of a patellofemoral implant. Inother words, the proximal portion 1202 of the two-in-one device 1300substantially represents the size and geometry of a portion of apatellofemoral implant.

The distal portion 1310 extending from the proximal portion 1302 has aplanar surface that is angled with respect to the bone interface surfaceof the proximal portion 1302 such that the distal portion 1310 extendsalong the trochlear region of the femur bone 100 when the proximalportion 1302 is engaged with the anterior resection of the femur bone100. The distal portion 1310 has a punch guide window 1312 that extendstherethrough and is dimensioned to receive the uniblade punch 1400. Thepunch guide window 1312 forms a rim along the perimeter of the punchguide window 1312. The rim is flanged and chamfered to allow for easyinsertion of the uniblade punch 1400 and to guide the uniblade punch1400 by accurately matching its shape. Along the rim is a plurality ofcutouts 1314 that form depressions in the rim. The distal portion 1310also has a bone contact surface. Material is removed from the bonecontact surface to allow for clearance of ostephytes and cartilage.Three spherical points are disposed on the bone contact surface toreference the most distal, medial and lateral points of which acorresponding implant would extend while in the same position.

Thus, the combined dimensions of the proximal portion 1302 and sphericalpoints of the distal portion 1210 of the two-in-one device 1300 providesan accurate representation of the periphery of a correspondingpatellofemoral implant in order to appropriately size the correspondingpatellofemoral implant.

FIG. 22 illustrates the initiation of a sizing step for the sizing of apatellofemoral implant. The surgeon places the two-in-one device 1300over the femur bone 100 such that the generally flat bone interfacesurface of the proximal portion 1302 of the two-in-one device 1300planarly engages the anteriorly resected portion of femur bone 100. Thealignment window 1304 located in the proximal portion 1302 providesvisual confirmation that the two-in-one device 1300 is fully seated andflush with the anterior resection. The distal portion 1310 is positionedover the trochlear region of the femur bone 100, and the sphericalpoints of the distal portion 1310 are placed into contact with the femurbone 100. The surgeon, at his or her discretion, determines if the sizeis appropriate for a corresponding patellofemoral implant. If not,another size may be tried until the appropriate size is determined. Oncethe appropriate size is chosen and properly placed on the femur bone100, the surgeon will insert retainment pins into the two-in-one device1400 through the retainment pinholes 1306. These retainment pins securethe two-in-one device from rotation and lift-off.

FIG. 24 shows the uniblade punch 1400 of the trochlear punch assembly3050. The uniblade punch 1400 generally has a handle 1404 with an impactregion 1402 disposed at one end of the handle 1404 and a transverse wall1406 disposed at the other end. The uniblade 1408 extends from thetransverse wall 1406 parallel to the longitudinal axis of the handle1404. The uniblade 1408 is generally curvilinear to substantially matchthe contours of a corresponding patellofemoral implant and the punchguide window 1312 of the two-in-one device 1300. The transverse wall1406 also has a plurality of tabs 1410 that extend from the transversewall 1410 in a direction generally perpendicular to the longitudinalaxis of the handle 1404. The plurality of tabs 1410 are configured andpositioned on the transverse wall 1406 such that they interface with thecutouts 1314 of the distal portion 1310 of the two-in-one device 1300during punching. The handle 1404 may be modular in order to interfacewith various punch sizes. However, the uniblade punch 1400 may beentirely monolithic.

FIG. 21 shows a trochlear punch step. With the two-in-one device 1300attached to the femur bone 100, the uniblade punch 1408 is inserted intothe punch guide window 1312 of the two-in-one device 1300. An impulseforce is applied to the impact region 1402. As the uniblade 1408penetrates the femur bone 100, the plurality of tabs 1410 engage thecutouts 1314 to provide added guidance and to act as a depth stop toprevent the uniblade 1408 from penetrating too deeply. Once the properdepth is achieved, the uniblade punch 1400 and two-in-one device 1300 isremoved from the femur bone 100 in preparation for further boneresection.

FIGS. 25 and 26 show a rimless drill template 1500 according to anembodiment of the present invention. The rimless drill template 1500 hasa bone interface surface and a plurality of holes extendingtherethrough. The plurality of holes include retainment pinholes 1504and drill guide holes 1506. The drill guide holes 1506 may be bossed andmay have a drill stop shoulder 1508 to act as a drill depth stop. Thelength of the boss is determined by the desired depth of cut. Thus, somedrill guide holes 1506 may not be bossed if greater depth is desired.The locations and number of the drill guide holes 1506 within therimless drill template 1500 directly correspond to the locations andnumber of bone pegs disposed on a corresponding rimless implant(discussed later). Generally there are at least two retainment pinholes1504 that have longitudinal axes that may be angled with respect to oneanother in order to prevent lift-off and rotation when coupled to thefemur bone 100. The bone interface surface may have peripheral flangesextending from the bone interface surface for engaging the section ofbone resected by the uniblade punch 1400. The periphery of the rimlessdrill template 1500 substantially matches the periphery of acorresponding rimless implant. In other words, the profile of therimless drill template 1500 is substantially similar to that of acorresponding rimless implant such that the surgeon has an accuratevisual representation of the size, shape and fit of the rimless implantwhen he or she drills via the circular rim drill template 1500. Thus,the rimless drill template 1500 provides the surgeon with an accuratedepiction of the rimless implant so that he or she can properly locatethe drill guide holes 1506 with respect to the femur bone 100.

FIG. 19 shows the initiation of a drilling step. The rimless drilltemplate 1500 is positioned onto the femur bone 100 such that theperipheral flanges are disposed within the bone void created by theuniblade punch 1400. A proximal portion of the bone interface surfaceplanarly engages the anterior resected portion of the femur bone 100.Rotation of the rimless drill template 1500 is set by the engagement ofthe peripheral flages with the uniblade punched portion of bone. Oncethe circular rimless drill template 1500 is properly seated, the surgeoninserts retainment pins into the retainment pinholes 1504 to prohibitmovement of the rimless drill template 1500 during drilling. The surgeonthen drills a series of holes into the femur bone 100 through the drillguide holes 1506 to a depth dictated by the drill guide holes 1506. Theretainment pins and rimless drill template 1500 is removed so that thecorresponding rimless implant may be implanted on the femur bone 100.

FIGS. 27-30 show yet other embodiments for preparing a femur bone 100 toreceive a patellofemoral prosthesis. FIGS. 27-29D illustrate a trochleartrajectory assembly (“TT assembly”) 3060. The TT assembly 3060 generallyincludes a monolithic trochlear trajectory finder (“monolithic TTF”)1600, a spiked sleeve 110, and alignment handles 400.

Referring to FIGS. 28A-29D, the monolithic TTF 1600 generally includeswings 1620, an alignment platform 1624, a first alignment hole 1602, asecond alignment hole 1614, a first reference pinhole 1606, a secondreference pinhole 1610, a posterior projection 1626 and a stylus 1616.The body is generally narrow compared to its thickness and may have ananterior surface 1612, an inferior surface 1604, a superior surface1628, a posterior surface 1630, a chamfer surface 1608 and L-M surfaces1622. The anterior surface 1600 and inferior surface 1604 are generallyorthogonal with respect to each other and separated by a chamfer surface1608. The first alignment hole 1602 extends from the inferior surface1604 into the monolithic TTF 1600. An alignment platform 1624, similarto that of the intercondylar block 200, is disposed adjacent to thefirst alignment hole 1602 extending from the inferior surface 1604. Thefirst reference pinhole 1606 extends into the chamfer surface 1608,while the second pinhole 1610 and second alignment hole 1614 extend intothe anterior surface 1612. The alignment holes 1602, 1614 preferably donot extend all the way through the monolithic TTF 1600, while the firstand second reference pinholes 1606, 1610 extend entirely through themonolithic TTF 1600. The longitudinal axis of the first alignment hole1602 is generally perpendicular to the anterior surface 1612, thelongitudinal axis of the first reference pinhole 1606 is perpendicularto the chamfer surface 1608, and the longitudinal axis of the secondalignment hole 1614 is perpendicular to the inferior surface 1604. Thelongitudinal axis of the second reference pinhole 1610 is oblique withrespect to the proximal surface 1612 and parallel to the longitudinalaxis of the first reference pinhole 1606. The first reference pinhole1602 has a larger diameter than the second pinhole 1610 in order toreceive the spiked sleeve 110. The first and second pinholes 1606, 1610are precisely located within the monolithic TTF 1600 such that referencepins 106 inserted through the first and second reference pinholes 1606,1610 may be used to align and guide other bone preparationinstrumentation, for example reamer 900 and captured resection guide1700 (discussed below).

A stylus extends 1616 from the superior surface 1628 and terminates at astylus tip 1618. At the other end of the monolithic TTF 1600, theposterior projection extends 1626 from the posterior surface 1630. Thewings 1620 extend from the L-M surfaces 1622. Referring to FIGS. 28A and28B, the monolithic TTF 1600 is shown superimposed over a patellofemoralimplant. The stylus tip 1618, the wings 1620, and the posteriorprojection 1626 represent the periphery of a patellofemoral implant asshown in FIGS. 28A and 28B. Thus, the stylus tip 1618, posteriorprojection 1626, and wings 1620 provide the surgeon with an accuraterepresentation as to the size and profile of a correspondingpatellofemoral implant.

The monolithic TTF 1600 may be used as an alternative trochlearreferencing scheme where sizing is the initial step. Further, themonolithic TTF 1600 is right and left knee specific with the wings ofthe monolithic TTF representing the widest M-L aspect of a trochlearregion of a patellofemoral implant. FIG. 27 shows a sizing and pininsertion step. Alignment handles 400 are placed in the first and secondalignment holes 1606, 1610. The monolithic TTF 1600 is placed onto thefemur bone 100 with the stylus tip 1618 planarly contacting the anteriorcortex just proximal of the trochlear groove, and the posteriorprojection 1626 placed along the trochlear groove. The surgeonrotationally aligns the monolithic TTF 1600 using the wings 1620 as avisual reference to represent the lateral and medial width of acorresponding patellofemoral implant. Once the surgeon determines theproper orientation and size, the spiked sleeve 110 is inserted into thefirst reference pinhole 1606. Spikes at the end of the spiked sleeve 110are impacted into the femur bone 100 to provide stability to themonolithic TTF 1600 while the surgeon inserts reference pins 106 througha passageway in the spiked sleeve 110 and into the second referencepinhole 1610. Once the reference pins 106 are inserted, the spikedsleeve 110 and monolithic TTF 1600 are removed from the femur bone 100,while the first and second reference pin 1606, 1610 remain.

The most distal reference pin 106 may be used as reference for thereamer 900 as previously described to form a bone void. Anteriorresection may then be performed by utilizing a captured resection guide1700. Alternatively, the trochlear punch assembly 3040 may be utilizedto punch the femur bone 100 prior to anterior resection.

FIG. 30 shows the captured resection guide 1700. The captured resectionguide 1700 generally includes a resection plate 1708, a restrictionplate 1706, a central post 1710, a cylindrical portion 1714, alignmentpinholes 1704, and cross pinholes 1712. The diameter of the cylindricalportion 1714 is determined by the diameter of the bone void formed bythe reamer 900. An alignment pinhole 1704 extends through the center ofthe cylindrical portion 1714 for reference to the most distal referencepin 106 located by the monolithic TTF 1700. The cylindrical portion 1714also has cross pinholes 1712 that extend through the cylindrical portion1714 at an oblique angle in order to provide added stability to thecaptured resection guide 1700 during resection. The resection andrestriction plates 1708, 1706 are attached to the face of thecylindrical portion 1714. The resection plate 1708 and restriction plate1706 are connected by a central post 1710 that may be triangular toprovide enhanced cutting angles. The restriction plate 1706 has analignment pinhole 1704 extending therein for reference to the proximalmost reference pin 106 located by the monolithic TTF 1700.

An anterior resection step may be performed by placing the alignmentpinhole 1710 of the cylindrical portion over the distal most referencepin 106 and the alignment pinhole 1704 of the restriction plate over theproximal most reference pin 106, thus providing rotational andanatomical alignment. The cylindrical portion 1714 is then inserted intothe bone void formed by the reamer 900. The resection plane may beoptionally demonstrated by the blade runner 700 as previously described.A bone saw is then used to resect the femur bone anteriorly through thegap between the restriction and resection plates 1706, 1708. Thecaptured resection guide 1700 may be removed from the reference pins 106to prepare for further bone preparation steps. Alternatively, thecaptured resection guide 1700 and reference pins 106 may be removed fromthe femur bone 100 for implantation of a circular rim implant.

FIGS. 31A-34D show various embodiments of a patellofemoral implant.These embodiments are merely exemplary and are not meant to beexhaustive of the possible variations. The patellofemoral implantgenerally includes an articular surface 1800, a bone contact surface1900, a distal region 1910, and a proximal region 1908. The articularcontact surface generally includes a lateral flange 1804 and a medialflange 1802. The intersection of the lateral and medial flange 1804,1802 forms a trochlear region 1806. The lateral flange 1804 sits prouderthan the medial flange 1802 in order to prevent patellar subluxation andto more closely conform to the contours of the natural knee for improvedpatellar tracking and to maintain the natural Q-angle. This enhancedgeometry is such that the patellofemoral implant is left and right legspecific. FIG. 31A shows an embodiment of the articular surface 1800 ofthe patellofemoral implant where the medial and lateral flange 1802,1804 have a steep drop to the resection level from an apex of the medialand lateral flange 1802, 1804. FIG. 31B shows another embodiment of thearticular surface 1800′ where the lateral flange 1804′ and medial flange1802′ tapers down to the resection level for a gradual transition tocartilage.

The bone contact surface 1900 generally includes a plurality ofprotrusions extending outwardly from the bone contact surface 1900 forinsertion into bone voids formed in the femur bone 100. The plurality ofprotrusions may include pegs 1916, 1922 a closed circular rim 1912, anopen circular rim 1918 or any combination thereof.

FIGS. 32A-34D show a preferred embodiment of the proximal region 1908,wherein the protrusions are three pegs 1916 extending from the bonecontact surface 1900 of the proximal region 1908. While three pegs 1916are shown, one or two pegs 1916 may also be utilized. The pegs 1916preferably extend from the bone contact 1900 surface of the proximalregion 1908 at a 45 degree angle with respect to the bone contactsurface 1900 in order to guide the patellofemoral implant into itsdesired location during implantation. However, peg angles from 15-60degrees may also be utilized. The locations of the pegs 1916 areoptimized for density and implant liftoff resistance. Each peg 1916 ispreferably the same length, however, peg lengths may vary to be within30% of each other.

FIGS. 32A-32D show one embodiment of a closed circular rim 1912embodiment of the distal region 1910. The closed circular rim 1912 isannular to form a cavity 1914 within the circular rim. The circular rimprovides a greater contact area between the patellofemoral implant, bonecement, and bone to aid in fixation. Further, the circular nature of theclosed circular rim 1912 inhibits the formation of hazardous stressconcentrations.

FIGS. 33A-33D show one embodiment of an open circular rim 1918embodiment of the distal region 1910′. The open circular rim 1918 is anannular feature that extends from the bone contact surface 1900′ of thedistal region 1910′ and is similar to the closed circular rim 1912 withthe exception of a cut-out 1920 in the open circular rim 1918. Thiscut-out 1920 may face the proximal region 1908′ as shown in FIGS. 33Aand 33C. However, the cut-out 1920 may also be a plurality of cut-outsthat are radially arrayed around the circumference of the open circularrim 1918 (not shown). The cut-out 1920 allows bone cement to flow out ofthe open circular rim 1918 once filled to ensure that the bone cementcan properly pressurize.

FIGS. 34A-34D show a rimless embodiment of the distal region 1910″.Rather than a rim, a peg 1922 extends from the bone contact surface1900″ of the distal region 1910″. The peg 1922 provides furtherstability and fixation while retaining a majority of the cortical bonein the trochlear region. The peg 1922 is preferably centered about thesaggital radius arc length as seen in FIGS. 32B-32D. However, it may beoffset from the center point of the sagittal radius arc by aboutplus/minus 20 degrees.

The patellofemoral implant may be provided in a multitude of sizes, forexample each embodiment described herein may be provided in four or moresizes, which are left and right leg specific, for a total of at leasteight patellofemoral implants per embodiment.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

The invention claimed is:
 1. A prosthesis for implantation within aprepared trochlear groove of a femur bone, comprising: a first regionhaving a first bone contact surface; and a second region having a secondbone contact surface, the second bone contact surface having an annulusprojecting outwardly therefrom for insertion into a bone void formed inthe femur bone, the annulus at least partially enclosing a base surfacehaving a boundary defined by the annulus, wherein a first plane definedby the first bone contact surface intersects a second plane defined bythe second bone contact surface, and wherein the annulus has alongitudinal axis intersecting the second plane.
 2. The prosthesis ofclaim 1, wherein the annulus includes a sidewall, and the sidewall andbase surface at least partially define a cavity for receipt of a boneadhesive.
 3. The prosthesis of claim 2, wherein the sidewall terminatesat a rim located further from the second bone contact surface than thebase surface.
 4. The prosthesis of claim 2, wherein the sidewallincludes at least one cut-out extending through the sidewall and beingin fluid communication with the cavity.
 5. The prosthesis of claim 4,wherein the at least one cut-out is a single cut-out that extendsthrough the sidewall from an interior surface thereof and out through anexterior surface thereof in a direction toward the first bone contactsurface.
 6. The prosthesis of claim 4, wherein the at least one cut-outand sidewall defines an open rim.
 7. The prosthesis of claim 4, whereinthe at least one cut-out is a plurality of cut-outs that are arranged ina radial array about a circumference of the sidewall of the annulus. 8.The prosthesis of claim 1, further comprising at least one protrusionextending from the first bone contact surface and having a longitudinalaxis intersecting the first bone contact surface.
 9. The prosthesis ofclaim 8, wherein the at least one protrusion is a cylindrical peg. 10.The prosthesis of claim 8, wherein the at least one protrusion is aplurality of cylindrical pegs spatially arranged in a triangular patternwithin the perimeter of the first bone contact surface.
 11. Theprosthesis of claim 1, wherein the second bone contact surface consistsessentially of the annulus.
 12. The prosthesis of claim 1, wherein thebase surface closes the annulus from one end thereof.
 13. A prosthesisfor implantation within a prepared trochlear groove of a femur,comprising: an articular side having an articular surface forming agroove for articulation of a patella; and a bone contacting side,disposed opposite the articular side, having first and second portionsand an annulus projecting from one of the first and second portions forinsertion into a bone void formed in the femur, the annulus at leastpartially enclosing a base surface having a boundary defined by theannulus.
 14. The prosthesis of claim 13, wherein the first portionincludes a planar bone contact surface for contacting an anteriorresected surface of the femur.
 15. The prosthesis of claim 13, whereinthe annulus includes a sidewall, the sidewall and base surface defininga cavity, the cavity having a depth extending between the base surfaceand an opening of the annulus and being configured to receive a cementmantle therein for fixation to the femur.
 16. The prosthesis of claim15, wherein a sidewall opening extends through the sidewall andcommunicates with the cavity.
 17. The prosthesis of claim 16, whereinthe opening faces the first portion of the bone contacting side.
 18. Aprosthesis for implantation within a prepared trochlear groove of afemur bone, comprising: an articular side having an articular surfacefor articulation of a patella; and a bone contacting side having firstand second portions adjacently disposed, the first portion having aplanar bone contacting surface for contacting a resected surface of afemur, the second portion having an annulus extending therefrom and abase surface, the base surface closing the annulus from one end thereof,and the base surface and annulus defining a cavity.
 19. The prosthesisof claim 18, wherein the first portion includes a plurality of elongatemembers projecting from the bone contacting surface.
 20. The prosthesisof claim 18, wherein the annulus incudes an opening in fluidcommunication with the cavity and extending from the cavity toward thefirst portion.